Temporal and Spatial Measurements of the Electron Density Perturbation Produced in the Wake of an Ultrashort Laser Pulse

Abstract

The plasma electron density oscillation produced in the wake of a narrow (beam waist $\ensuremath{\ll}$ plasma wavelength) ultrashort laser pulse is measured for the first time, with a temporal resolution much better than the electron plasma period and a high spatial resolution along the laser focal spot diameter. The relative density perturbation is between 30% and 100%, in good agreement with numerical simulations.